Leishmania species are hemoflagellate protozoa which are transmitted by the bite of the sandfly. In man, the organisms grow and multiply in tissues of the reticuloendothelial system. Some of these species of parasites of genus Leishmania cause cutaneous lesions which usually appear as chronic, ulcerative skin lesions. Dermotropic species like L. tropica, L. aethiopica, and L. major are most prevalent in the Old World, while L. peruviana, L. mexicana, L. guvanensis, L. amazonensis, L. panamensis, and L. braziliensis are found in the New World. L. panamensis and L. braziliensis may metastasize to the oral-nasal mucosa to cause mucosal leishmaniasis. Both L. aethiopica and L. mexicana cause diffuse cutaneous leishmaniasis. No vaccine or other prophylaxis against these diseases is currently available.
Drugs most commonly used against these parasites contain the pentavalent antimony. The sodium stilbogluconate (Pentostam) and the meglumine antimonate (Glucantime) are commonly used. These drugs are toxic to the liver, kidneys, pancreas and heart. The most serious effects are pancreatitis and cardiac arrhythmias. Amphotericin B and Pentamidine are also used, but are equally toxic. Ketocanazole is effective against some species. The present treatment of choice required injections of pentavalent antimonies for 10-28 days under hospital care, since such treatment often results in side effects such as cardiac arrhythmias, pancreatitis and hepatitis.
U.S. Pat. No. 4,595,901 to El-On, et al. discloses a composition containing a mixture of paromomycin or a salt thereof with dimethylsulfoxide or quaternary ammonium salts, especially methylbenzethonium chloride. These compositions are effective against some Leishmania species, but are ineffective against others. The compositions of that patent have been found to be essentially ineffective against most New World strains and against some of the Old World strains. Gentamicin was tried in some of the El-On compositions, but was essentially ineffective when formulated in accord with the teaching of El-On. The claimed compositions of El-On are toxic to many patients when given at therapeutic levels.